The continuing crackdown follows confirmation from a Saudi cell of the Al-Qaeda terrorist network that its leader, Abdulaziz al-Muqrin, and three other militants have been killed by Saudi security forces in Riyadh.

Saudi officials are calling Al-Muqrin's death a "major blow" against Al-Qaeda. But the terrorist network says it will fight on under new leadership and that Al-Muqrin's death has merely increased the determination of other militants to wage jihad.

The Al-Qaeda statement was posted on the same website that released photos on 18 June showing the beheaded American hostage Paul Johnson, a civilian contractor for the U.S. defense firm Lockheed Martin. The website also is continuing to display video footage it released earlier this month of a masked gunman, thought to be Al-Muqrin, who says recent attacks against foreigners are in revenge for violence against Muslims by U.S. military forces in Iraq and Afghanistan:

"You crusaders have gathered against the Muslims and killed the old and the children, and raped women, and stole the money and fortunes of Muslims," the purported voice of Al-Muqrin said.

Saudi state television yesterday broadcast pictures of four bloodied corpses and named one of the dead men as Al-Muqrin -- Saudi Arabia's most-wanted man. Saudi authorities said the other three were associates of Al-Muqrin and also had been involved in the recent surge of violence against foreigners in Saudi Arabia.

The four Al-Qaeda fighters reportedly were killed in a shootout the night of on 18 June while trying to dispose of the body of Johnson. Saudi officials say 12 other members of Al-Muqrin's Al-Qaeda cell also were captured - including one senior militant believed to have been involved in the 2000 bombing of the warship "U.S.S. Cole" off the coast of neighboring Yemen.

Adel al-Jubeir, a foreign affairs adviser of the Saudi crown prince, spoke to reporters in Washington last night about the developments:

"[The capture and killing of Al-Muqrin and his associates] happened, unfortunately, after [U.S. hostage] Mr. [Paul] Johnson was murdered," Al-Jubeir said. "I wish we had captured them before they abducted him. I wish we had captured them before they murdered him. But that's not how it happened. And we just have to deal with the situation as it unfolds."

Al-Jubeir refuted earlier reports that Johnson's body had been recovered by Saudi officials:

"The body has not been recovered. There was confusion about this issue. The determination that Mr. Johnson was murdered was made on the basis of technical analysis of the [images on the Al-Qaeda website] by both U.S. and Saudi experts," Al-Jubeir said. "We are searching for [Johnson's] body. We believe we know the area in which the body might be on the northern outskirts of Riyadh. But we haven't found the body yet."